1. Field of the Invention
The present invention relates to a process for the metathesis of olefins and functionalized olefins on Re.sub.2 O.sub.7 /Al.sub.2 O.sub.3 -containing catalysts in which process activators are used.
2. Description of the Background
The metathesis of olefinic hydrocarbons is used in the manufacture of specific olefins, dienes and polyenes and unsaturated polymers. Even olefins with functional groups are subject to the metathesis reaction provided suitable catalysts are used. In so doing, of special importance is the metathesis of unsaturated fatty acid methyl esters, which are produced on a large scale by transesterifying native fats and oils with methanol and are thus commercially available as parent compounds. The metathesis of these esters opens a new and simple access to intermediate products through chemical engineering for the commercial production of surfactants, plastics, plasticizers, lubricants and a whole range of fine chemicals.
Warwel, Erdol-Erdgas-Kohle, Petroleum, Natural Gas, Coal, Vol. 103 (1987), pp. 238-45, describes industrial metathesis procedures, wherein predominantly Re.sub.2 O.sub.7 /Al.sub.2 O.sub.3 -, CoO-MoO.sub.3 /Al.sub.2 O.sub.3 and WO.sub.3 /SiO.sub.2 catalysts are used. According thereto, only the Re.sub.2 O.sub.7 /Al.sub.2 O.sub.3 catalyst is already active at room temperature. Generally, tin alkyls are added as the activators of the catalysts.
According to FR 2 521 872 during metathesis lead tetraalkyls can also be added as the activators.
To date organoaluminum compounds have not been recommended as activators. Bosma et al., Journal of Organometallic Chemistry, Vol. 255 (1983), pp. 159-71, did test a number of organometallic compounds and, in so doing, also (CH.sub.3).sub.3 Al.sub.2 Cl.sub.3, but it was found that the activating effect of this organoaluminum compound is very low.
For specific applications of olefinic compounds prepared through olefin metathesis, such as in the pharmaceutical or cosmetic industries, for example, the use of tin and lead alkyls as activators for metathetical catalysts is impractical for physiological reasons. Notably, these organometallic compounds or their successor products may remain in small quantities in the olefinic reaction mixture following the separation of the heterogeneous rhenium oxide contact and, therefore, remain in the final product employed in commerce.